1. Field of the Invention
The present invention relates to a throttle valve control device for internal combustion engines, and more particularly to a throttle valve returning mechanism for the throttle valve control device.
2. Description of the Prior Art
In general, a throttle valve control device of this type is constructed so that a control signal corresponding to an angular movement of an acceleration foot pedal is applied to a drive means to thereby adjust an opening degree of the throttle valve.
In the throttle valve control device shown in, for example, Japanese Patent Examined Publication No. 25853/1983, an electromagnetic clutch mechanism is disposed between a throttle valve shaft and a driving means, and the throttle valve is controlled by the driving means during the operation of the electromagnetic clutch mechanism. The electromagnetic clutch serves as a safety device, so that, if any operational failure is encountered in the driving means or the like, the clutch causes the throttle valve to be free from the control and the throttle valve is closed by a throttle valve closing spring.
However, in such a device, since the drive means must drive the throttle valve against the valve closing force of the throttle valve closing spring, an opening responsibility of the throttle valve tends to be slow. Efforts should be made to overcome this shortcoming.